Four million people world wide suffer from inflammatory bowel disease (IBD), in the form of Crohn's disease or ulcerative colitis. More than 600,000 people in the US suffer from some form of IBD, costing up to $1 billion in missed work per year. Moreover, IBD is associated with increased risk for colon cancer. Colorectal cancer is the second leading cause of cancer death in the US and Canada (National Cancer Institute, 2005; Canadian Cancer Society, 2006). 148,610 new cases of colon cancer in 2006 were projected in the US alone, with the cost of colorectal cancer treatment reaching $8.4 billion (in 2004 dollars) per year (NCI, 2005). In 2008, nearly 150,000 Americans will be diagnosed with colorectal cancer and 50,000 of those will die from colon cancer (American Cancer Society, 2007). The cost-effectiveness benefits for screening, compared with no screening, range from $10,000 to $25,000 per life year saved (National Committee for Quality Assurance, 2004).
Currently, colonoscopy is the most sensitive test for diagnosing IBD and screening for colon cancer. In colonoscopy, a flexible endoscope is used to examine the inner wall of the entire length of the large intestine, from the rectum to the caecum. Even though colon cancer is 90% successfully treated if detected at an early stage, the compliance rate for screening is only 30% in the United States. This resistance to regular colonoscopies is due, in large part, to the fact that the procedure is extremely uncomfortable. The uncomfortable nature of the procedure is due, in part, to the trial-and-error manipulations of the scope in order to navigate the flexible and elastic colon. In particular, loops can form in the flexible endoscope anywhere along the length of the scope. Loops can inflict a great deal of pain and discomfort on the patient. Loops can also lead to physician disorientation in the colon, resulting in misdetection of lesions and incorrect localization that can lead to unnecessary patient pain and suffering. In addition, the procedure may be abandoned before its completion due to difficulty in ‘near-blind’ navigation. The lack of full visual guidance in these procedures is often the bottleneck in the completion of colonoscopy procedures. Therefore, a robust tracking and guidance system that can provide position and shape information for the colonoscope is needed.